Abstract

This paper demonstrates an application of the nine linear accelerometer scheme, proposed by (Padgaonkar et al., 1975), to the development and validation of a finite element model of a deformable featureless headform for rotational accelerations. Steps and procedures involved in the development and calibration of the model are also described. A set of tri-axial accelerometers was mounted at the headform center of gravity, C.G., which is located at the origin of the local coordinate axes of the headform. Three bi-axial accelerometers were also mounted at the front, left, and top of the headform’s aluminum skull and on the local coordinate axes of the physical headform. Nine linear accelerations were measured at the headform in drop tests against a rigid plate at impact speeds of 2.68, 4.0, 5.36, and 6.71 m/s (6, 9, 12, and 15 mph). The rotational accelerations of the headform were then calculated from the nine linear acceleration measurements. In the finite element (FE) model of the featureless deformable headform, a visco-elastic material law, available in the non-linear dynamic explicit code PAM-CRASH, was used to simulate the vinyl skin response during impact. The constitutive parameters of the headform’s skin material were calibrated through comparison of the headform drop simulations at various impact speeds with the corresponding tests. Headform responses, such as, resultant acceleration time histories at the headform C.G. and the rotational acceleration time histories obtained from the FE predictions of the headform responses during the drop tests simulations correlated very well with those obtained from experiments. Validation of the headform model for rotational accelerations provided higher level of confidence in the prediction capability of the model when used for interior head impact simulations with vehicle upper interior as specified by the Federal Motor Vehicle Safety Standard FMVSS 201.

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